Uterine and peripheral plasma F-prostaglandins correlated with peripheral progesterone in cyclic rats

Abstract

Radioimmunoassay (RIA) measurements of F-prostaglandins (PGF) were made in uterine venous and peripheral venous plasma. RIA determinations of progesterone (P) were also made in the peripheral venous plasma from the same rats. Concentrations of PGF in uterine venous plasma were lowest between 1000–1200 h of estrus (6.07 ng/ml), peaked at metestrus between 1000–1200 h (12.50 ng/ml), decreased on the day of diestrus between 1000–1200 h (10.25 ng/ml) and continued to decline at 1000–1200 h of proestrus (8.48 ng/ml). Thereafter there was a significant increase in the values between 1400–1600 h (10.54 ng/ml) which by 1900–2100 h had dropped again (7.17 ng/ml) and remained unchanged between 2300-0100 h. Between 0200–0400 h on the day of estrus, however, the values again showed a significant increase at the time when most of the animals ovulated. The first peak concentration of PGF in the peripheral venous plasma was also recorded between 1000–1200 h of metestrus, but was not significantly different from the values recorded on the day of diestrus and proestrus between 1000–1200 h. The second peak occurred at the same time as that recorded in uterine venous plasma. The lowest levels of progesterone were between 1000–1200 h on the day of proestrus (17.97 ng/ml). Then the values began to rise reaching a peak (46.14 ng/ml) between 1900–2100 h. Thereafter the values declined. This drop was associated with increase in both peripheral and uterine PGF.